There are many devices for providing musical data.
These devices are generally limited to providing relatively incomplete musical data taken in isolation without information as to their compatible or coherent harmonic context, i.e. respect for the fundamental rules of harmony, such as sequences compatible with the fundamental rules of harmony. The rules of harmony are principally the rules governing the sequence of notes or chords, i.e. the data concerning the notes or chords that precede or follow a given note or chord in a manner considered musically compatible.